The present invention relates to a tripod joint, and more specifically, to a tripod joint with an outer joint part having three circumferentially distributed axis-parallel recesses which form circumferentially opposed tracks. An inner joint part has a star-shaped cross-section and three circumferentially distributed arms which engage the recesses of the outer joint part. The arms hold roller assemblies which each include a roller carrying means and a roller directly riding on the tracks. On each arm, a roller carrying element is held so as to be axially and angularly movable relative to the arm axis. Also, on each roller carrying element, a roller is axially secured and rotatably supported via a rolling contact bearing.
Known tripod joints are described in DE 28 31 044 (Honda), and DE 39 36 601 (GKN) for example. In both cases, the roller, especially via a needle bearing, is rotatably supported on a roller carrier. The roller carriers are arranged to be axially movable on the arm and pivotable relative to the arm axis.
In the first design, movability is achieved via an inner ring which, via a spherical outer face, engages an at least partially internally spherical inner face of the roller carrier. The inner ring is designed to be internally cylindrical and with a cylindrical arm being axially movable therein.
In the second case, the roller carrier is provided with an internally cylindrical inner aperture, which is axially movably and pivotably engaged by an arm with a part-spherical outer end.
Below, all parts of the "roller assembly" with the exception of the "roller" itself will be referred to as "roller carrying means". The expression "elements of the roller assembly" refers to the "roller carrier" and the "roller" itself, with the "roller carriers" being regarded as "non-rotating elements of the roller assembly".
With a joint rotating in the articulated condition, there occurs, with reference to the inner joint part, radially oscillating movement of the rollers relative to the joint axis and pivoting movement of the rollers on the arms. At the same time, with reference to the outer joint part, there occurs longitudinally extending oscillating rolling movement of the rollers along the tracks. The first mentioned radial and pivoting movements are accompanied by sliding friction. The next mentioned rolling movement predominantly occurs in the form of rolling contact movement. As a result of the friction forces, the prior art tripod joints, with an increasing joint articulation angle, are characterised by an increase in the joint excitation forces, e.g. in the cyclic forces generated in the joint and transmitted to the driveline. If, as a result of the movements occurring when the joint rotates in an articulated condition, an arm, with reference to the outer joint part, is displaced radially inwardly, with the roller having to support itself radially inwardly relative to the outer joint part, the sliding friction forces are particularly high and disadvantageous. In particular, this applies to sliding friction forces caused by supporting forces resulting from tilting moments around axes at the roller assemblies assumed to be located transversely relative to the joint axis.